The present technology relates to a solid-state imaging device, a driving method thereof, and an electronic device such as a camera or the like including the solid-state imaging device.
A CMOS (Complementary Metal Oxide Semiconductor) solid-state imaging device is known as a solid-state imaging device (image sensor). The CMOS solid-state imaging device is used in various portable terminal devices and the like including digital still cameras, digital video cameras, and portable telephones provided with a camera.
Many CMOS solid-state imaging devices known in the past transfer the charge of a photodiode (PD) serving as a photoelectric conversion section to a floating diffusion section (FD), and extract a pixel signal by reading the potential of the floating diffusion section. In this case, when the floating diffusion section has a low capacitance, a gain with which conversion into voltage is made is increased, and subsequent noise appears to be low. Thus, a good S/N is obtained. However, an amount of charge that can be handled is small. Conversely, when the floating diffusion section has a high capacitance, the amount of charge that can be handled is increased, but the S/N is lowered.
A solid-state imaging device in which a floating diffusion section is formed by two capacitances is proposed to solve a tradeoff relation between the amount of charge handled and the S/N. The solid-state imaging device is configured to use a signal (S1) read by one capacitance (FD1) when there is a small amount of charge and use a signal (S2) read by two capacitances (FD1 and FD2) when there is a large amount of charge. Japanese Patent Laid-Open No. Sho 63-67976, JP-T-2009-505498, and PCT Patent Publication No. WO2005/083790 (referred to as Patent Documents 1, 2, and 3, respectively) disclose examples of such solid-state imaging devices in the past.